Removing the JBD or vice versa will cause a skewed result until your DME adapts.

Indeed. Usually I see a 5 mpg spread that narrows itself down to 2 over time. This time, its been a 10 mpg spread, but its probably über-confused considering that it went from JBD 100% to no JBD to recall W/out JBD to recall with JbD. She'll firgure it out eventually.